My kids love listening to music in the car. They mostly ride around with my husband, but whenever they are in the car with me, I have to stop listening to NPR (because I don't want to freak the kids out) and listen to music. They love anything that we listen to and so as they have gotten older, we have had to be a little more picky about what we listen to with them (no more Kanye, which was A's favorite when he was a newborn).
Right now, their favorite song is "Ho Hey" by the Lumineers (A calls it "Hee Ho"). When we drive across town, A insists on hearing that song over and over again. Luckily we like it too, despite hearing it a million times. A has the song memorized. There is something very sweet about a 3 year-old singing at the top of his lungs, "I belong with you, you belong with me, you're my sweetheart".
Here is a great link to the benefits of listening to music with your kids while driving around and other things you can do with your kids in the car to build early literacy skills: Reading Activities in the Car.